The following error in Ver 1.3 SDK, has also been in all previous SDK versions of P3D, ESP & FSX

These TRANSPONDER Events should all be documented as "All aircraft"

KEY_XPNDR_1000_INC XPNDR_1000_INC Increments first digit of transponder  Shared Cockpit
KEY_XPNDR_100_INC XPNDR_100_INC Increments second digit of transponder  Shared Cockpit
KEY_XPNDR_10_INC XPNDR_10_INC Increments third digit of transponder  Shared Cockpit
KEY_XPNDR_1_INC XPNDR_1_INC Increments fourth digit of transponder  Shared Cockpit
KEY_XPNDR_INC_CARRY XPNDR_INC_CARRY Increments fourth digit of transponder, and with carry. Shared Cockpit 

KEY_XPNDR_1000_DEC XPNDR_1000_DEC Decrements first digit of transponder  Shared Cockpit
KEY_XPNDR_100_DEC XPNDR_100_DEC Decrements second digit of transponder  Shared Cockpit
KEY_XPNDR_10_DEC XPNDR_10_DEC Decrements third digit of transponder  Shared Cockpit
KEY_XPNDR_1_DEC XPNDR_1_DEC Decrements fourth digit of transponder  Shared Cockpit
KEY_XPNDR_DEC_CARRY XPNDR_DEC_CARRY Decrements fourth digit of transponder, and with carry. Shared Cockpit

Below, is the only Transponder Event that is Documented Correctly

KEY_XPNDR_SET XPNDR_SET Sets transponder code (BCD) All aircraft 

Thanks Adam ... at least this one is an easy fix